Communications Network

ABSTRACT

A distributed Internet Protocol communications network comprises a central control system comprising control processing means and at least one access point remote from the central control system for providing access to the packet based communications network. Under normal operating conditions the at least one access point is controlled by the control processing means. The network also comprises an emergency processing distinct from the central control system for controlling the lease one access point when there is a failure in the control processing means control of the at least one access point.

In the past, large companies having a corporate headquarters and multiple branch offices have tended to operate independent self-contained telecommunication systems at each of the branches and at the headquarters. Naturally, these independent systems would be networked together. The administrative effort and the costs involved in running such multiple independent systems was high.

More recently, by using Internet Protocol (IP) internetworking between the headquarters and the various branches, it has been possible to relocate parts of the headquarters central system into the branches, whilst retaining a single point of control at the headquarters.

Systems based on the HiPath 4000 IP Distributed Architecture, provided by Siemens AG, are examples of such IP internetworked systems. An example of a HiPath 4000 IP Distributed Architecture system is shown schematically in FIG. 1.

Telecommunication system 1 comprises a first Local Area Network (LAN) 2 located at a company's headquarters, a second LAN 3 located at a first branch office (not shown), a third LAN 4 located at a second branch office (not shown) and a fourth LAN 5 located at a third branch office (not 5 shown). The first LAN 2 is connected to a first router 6, the second LAN 3 to a second router 7, the third LAN 4 to a third router 8 and the fourth LAN 5 to a fourth router 9. These routers connect the LANs via a Wide Area Network (WAN) 10.

A first access point 11 connects to the first Lan 2, a second access point 12 connects to the second LAN 3, a third access point 13 connects to the third LAN 4 and fourth 14 and fifth 15 access points connect to the fourth LAN 5. These access points 11 to 15 allow the connection of client terminals (not shown) to the LANs 2 to 5 and hence to the WAN 10. In a typical HiPath 4000 system the client terminals may either be traditional Time Division Multiplexed (TDM) devices, for example standard telephones or cordless telephones, or IP devices, for example IP telephones.

A central control system 16 connects to the first LAN 2 at the headquarters (not shown) and is responsible for controlling the operation of each of the access points 11 to 15.

Each of the access points 11 to 15 comprises a respective gateway card 11 a to 15 a and a plurality of peripheral cards 11 b to 15 b. The peripheral cards 11 b to 15 b provide multiple peripheral ports for connection to client terminals, for example phones and/or trunk lines. The gateway cards 11 a to 15 a are the controllers of the IP based Access Point. Each of the cards 11 a to 15 a acts as a gateway between the LAN on one side of the card, and the client terminals on the other side of the card, converting payload data (e.g. voice data, fax data and ISDN-data) from TDM data to IP data and vice versa. Each of the cards 11 a to 15 a provides a local TDM switching matrix, conference units and tone generators. Each of the gateway cards 11 a to 15 a may be Siemens' HG 3575 cards.

The central control system 16 comprises a plurality of gateway cards 16 a, a plurality of peripheral cards 16 b, an administration and data processor 16 c, a common control processor 16 d and a back up common control processor 16 e.

Again, the plurality of peripheral cards 16 b provide multiple peripheral ports for connection to client terminals, for example phones and/or trunk lines. The gateways 16 a translate payload data (voice/fax/ISDN-data) from TDM data on the client terminal side of the gateways to IP data on the LAN side of the gateways and vice versa. These gateways are used for connections between the IP based access points 11 to 15 and the central system 16. These cards 16 a may be Siemens' HG 3570 cards.

The Administration and Data Processor 16 c runs administrative software and applications, whilst the common control processor 16 d runs call processing software. The back up common control processor 16 e provides a back up to the common control processor 16 d and in the event of the failure of the common control processor 16 d, it can be switched into use without interrupting active calls.

The access points are controlled by the common control processor 16 d. Every activity of the peripheral cards, for example, tones or displays at the phones and signaling messages at trunk interfaces are controlled by the common control processor 16 d via a control link over the IP network. A complete set of administrative parameters in a database (not shown) in the central system 16 is kept in the memory of the control processor 16 d. A persistent copy of the database is kept on hard disc which is controlled by the administration and data processor 16 c.

Such systems have reduced administrative outlay but an increased dependence on the availability of the network and of the central system. If the central control fails, no further telecommunication is possible—in the corporate HQ or in the branches. A very high availability of the central control is achieved by duplicating the control processors.

As illustrated in FIG. 2, in order to maintain control of access points upon failure of the WAN 10, a modem connection may be established between the central system 16 and some or all of the access points. In FIG. 2, a connection between the central system 16 and the third access point 13, the fourth acess point 14 and the fifth access point 15 is made through the Public Switched Telephone Network (PSTN) 17 via a router 18 connected to the LAN 2 and a first modem 19 connected to the gateway 13 a, a second modem 20 connected to the gateway 14 a and a third modem 21 connected to the gateway 15 a. Access points without modem connections, in this example, the second access point 12, go out of service when their WAN connections fail. However, even back up systems such as this are useless in the event of total failure of the central system brought on by a catastrophy such as flooding or destruction of the building.

Embodiments of the present invention aim to alleviate the above described problems.

According to the present invention there is provided a distributed packet based communications network comprising: a central control system comprising control processing means; at least one access point remote from the central control system, the at least one access point for providing access to the packet based communications network, wherein under normal operating conditions the at least one access point is controlled by the control processing means; and emergency processing means distinct from the central control system for controlling the at least one access point when there is a failure in the control processing means control of the at least one access point.

The above and further features of the invention are set forth with particularity in the appended claims and together with advantages thereof will become clearer from consideration of the following detailed description of an exemplary embodiment of the invention given with reference to the accompanying drawings, in which:

FIG. 1 illustrates a communication system and has already been described;

FIG. 2 illustrates a communication system and has already been described;

FIG. 3 illustrates a communications system embodying the present invention.

Referring now to FIG. 3 of the drawings, in which identical features as those illustrated in FIG. 1 are given like reference numerals, a communications system 100 embodies the present invention.

Under normal operating conditions the communications system 100 functions identically to the system 1 illustrated in FIG. 1. That is to say, the four access points 11 to 15 are all operated under the central control of the central system 16.

The system 100 is provided with an emergency de-centralised control system for controlling access points in the event of the failure of the IP network linking access points and the central system 16 or if the central system 16 is not actually available. To this end, the first access point 11, the third access point 13 and the fourth access point 14 are provided with their own emergency control processors labelled 11 c, 13 c and 14 c respectively.

Each of the emergency control processors 11 c, 13 c and 14 c offer the same functionality as the central control. They possess the same software, the same patch status (i.e. software corrections applied to the system while running) and identical configuration data as do the administration and data processor 16 c and the common control processor 16 d of the central system 16. Groups of access points are assigned to emergency control groups, each emergency control group comprising one of the emergency control processors 11 c, 13 c and 14 c. In the system 100, the first access point 11 and the second access point 12 makeup a first emergency control group, the third access point 13 makes up a second emergency control group and, the fourth access point 14 and fifth access point 15 make up a third emergency control group. Each of the emergency control processors 11 c, 13 c and 14 c is in contact with the the gateway cards in its respective emergency group. Thus, if an access point of an emergency group loses contact with the central system the emergency processor of that group may take control of the access point.

A mechanism is provided for keeping the software status and the configuration data of the emergency control processors identical to that of the central system 16.

A backup server 22 is connected to the WAN 10, and in order to save on transmission bandwidth the software the software and database of the central system 16 is transmitted periodically, for example each day, to the backup server 22. This backup server 22 is as a general rule a separate device from the central system 16 and the emergency control processors 11 c, 13 c and 14 c. The central system 16 and all the emergency control processors 11 c, 13 c and 14 c have access via the IP network 10 to the backup server 22. The emergency control processors 11 c, 13 c and 14 c check cyclically whether updated data is present on the server 22 and download it where necessary. Thus each emergency control processor maintains an identical database to that at the central control. In an emergency the emergency control processors 11 c, 13 c and 14 c can thus behave in exactly the same way as the central system processors.

A fault occurs when an access point can no longer be served by the central control 16. If an access point gateway card detects a problem with the signalling connection between the access point of that card and the central system 16, it reports that fact to the emergency processor of the emergency group to which the access point belongs. The emergency processor decides according to preconfigured rules whether to take over control of the access point or not. In one embodiment, each access point in an emergency group is assigned a weight value of between zero and one, and when the total weight value of all access points in the emergency group that have lost connection with the central system 16 equals or exceeds a predefined threshold, the emergency processor of the group takes over control of those access points. So for example, in an emergency group comprising three access points each having a weight value of 0.5 and wherein the threshold is 1, it is only when at least two access points have reported a central system connection failure that the emergency processor steps in and assumes control of those access points. Naturally, an individual access point of particular importance, for example an access point serving the telephones of senior managers, may be assigned a weight value equal to the threshold value so that if this access point loses connection with the central system, an emergency processor immediately assumes control of it.

In alternative embodiment, the access points in an emergency group may be configured to be taken over individually by the group's emergency processor as and when an access point loses contact with the central system 16.

Naturally, the access points may be configured so that an immediate hand over to an emergency processor may be ordered by the system administrator.

In a preferred embodiment, to take over control of an access point, the emergency processor instructs the gateway card of the access point to restart and to start up with the emergency processor.

If the central system 16 succedes in re-establishing a control connection to an Access Point in emergency operation, the access point remains under the control of the emergency processor but notifies it that it has re-established contact with the central system 16. The emergency processor decides in accordance with pre-defined rules whether and when emergency operation can be ended.

For example, emergency control may be ended only if every access point in an emergency group has had a stable connection with the central system 16 for a configurable pre-determined time period. Emergency control may only be ended at configurable pre-defined times of the day. The system may be configured so that a system administrator may order the end of emergency control.

To end emergency control of an access point, the emergency control processor instructs the gateway card of the access point to do a restart and to start up under the control of the central system 16.

Having thus described the present invention by reference to preferred embodiments it is to be well understood that the embodiments in question are exemplary only and that modifications and variations such as will occur to those possessed of appropriate knowledge and skills may be made without departure from the scope of the invention as set forth in the appended claims. 

1.-9. (canceled)
 10. A distributed packet based communications network, comprising: a central control system comprising a central controller; an access point remote from the central control system, the access point provides access to the packet based communications network, wherein under normal operating conditions the access point is controlled by the central controller; and an emergency controller distinct from the central control system and which controls the access point when there is a failure in the control of the access point by central controller.
 11. The system according to claim 10, wherein the emergency controller includes the same functionality of the central controller.
 12. The system according to claim 11, further comprising a server to which data from the central control system is uploaded for downloading to the emergency controller in order for the emergency controller to maintain the same functionality as the central controller.
 13. The system according to claim 12, wherein the server is distinctly separate from the central control system and the access point.
 14. The system according to claim 13, wherein the data is uploaded periodically.
 15. The system according to claim 11, wherein upon detection of a failure of the control of the access point, the emergency controller determines whether to take control of the access point based upon predetermined rules.
 16. The system according to claim 11, wherein the access point provides TDM. user terminals access to the packet based communications network.
 17. The system according to claim 11, further comprising a plurality of access points forming a group of access points, wherein the emergency controller controls any of the access points in the group when there is a failure in the control of any of the access points in the group.
 18. The system according to claim 17, comprising a plurality of groups of access points, each group comprising an emergency controller for controlling any of access points in the group when there is a failure in the control of one or more access points in the group.
 19. The system according to claim 11, comprising a plurality of groups of access points, each group comprising one or more access points and an emergency controller for controlling any of the one or more access points when there is a failure in the control of one or more access points in the group.
 20. An emergency controller in a packet based communication network, comprising: a software for controlling an access point when a failure occurs in a central controller, the central controller distinct from the emergency controller and controls the access point under a normal operating conditions, the access point provides access to the packet based communication network; a data having control information to be used by the software in order to control the access point; and a failure indicator that indicates if the failure occurs, wherein the emergency controller cyclically polls a server for an update to the data, the server distinct from the emergency controller, and wherein the software uses the data to control the access point in response to the failure indicating that the failure occurred.
 21. The emergency controller as claimed in claim 20, further comprising a restore indicator that indicates that the control is to be restored to the central controller.
 22. The emergency controller as claimed in claim 21, wherein the emergency controller polls the server for an update to the software.
 23. An access point for providing access to a packet based communication network, comprising: a gateway card; an emergency controller, comprising: a software for controlling an access point when a failure occurs in a central controller, the central controller distinct from the emergency controller and controls the access point under a normal operation, a data having control information to be used by the software in order to control the access point; an interface to a server that is distinct from the access point and from the central controller; and wherein in response to detecting the failure, the emergency controller instructs the gateway card to restart under the control of the emergency controller.
 24. The access point as claimed in claim 23, wherein in response to detecting a recovery, the emergency controller instructs the gateway card to restart under the control of the central controller.
 25. The access point as claimed in claim 24, wherein the emergency controller cyclically polls the server for an update to the data.
 26. The access point as claimed in claim 24, wherein the emergency controller polls the server for an update to the software.
 27. The access point as claimed in claim 24, wherein in addition to detecting the failure, a criterion must be met in order for the emergency controller to instruct the gateway card to restart under the control of the emergency controller. 